ScienceDaily reports: A microchip about the size of a grain of rice can generate a highly organized "rainbow" of light, a capability that could eventually support faster, higher-capacity 6G communications and extremely precise timing for quantum technologies. Physicists at Loughborough University, working with an international research team, demonstrated a system that produces a series of precisely spaced light frequencies. Those optical frequencies can then be converted into multiple high-frequency electromagnetic signals known as millimeter waves. Millimeter waves are attracting growing interest for future communications because they can provide considerably more bandwidth, giving networks more room to transmit data. A major obstacle, however, has been producing these signals with the precision and stability required for advanced applications... "They could ultimately contribute to faster, higher capacity 6G networks," [said Dr. Luke Peters, of Loughborough University's Emergent Photonics Research Centre], "but the potential goes far beyond communications. These frequencies could also be used in radar systems as well as spectroscopy and astronomical instruments, helping scientists study materials and make extremely precise measurements of the universe. "These applications are still some way off, and there are challenges to overcome before the technology can be used in real-world systems — but our latest work has tackled a major one..." A microcomb generates an extremely precise set of light frequencies arranged somewhat like the colors in a rainbow, although the light itself is invisible to the human eye. A specialized antenna can then convert those optical frequencies into millimeter waves. Earlier research demonstrated that microcombs could produce a single precise millimeter wave frequency. Generating many frequencies simultaneously could be far more useful because each could potentially serve as a separate channel for transmitting information at the same time. Achieving that, however, requires a microcomb with exceptional stability and signal quality. In a new Nature Communications paper, the Loughborough led researchers report a system capable of doing exactly that. Their system connects its chip-based microresonator to a much larger loop of optical fiber where laser light continuously travels through both parts of the system, according to the article. "The team is now investigating how the microcomb system could eventually move from a laboratory experiment into practical technology."

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Coupure gouvernementale ou accidentelle, panne massive d’électricité, catastrophe naturelle… L’accès à Internet est exposé à toutes sortes de défaillances. D’où l’idée de créer des modes de communication indépendants, les réseaux maillés. À Seattle, ce projet rassemble un nombre croissant de personnes.

© SOURCES : MESHCORE NODE MAP (MESHCORE.IO) ; “LE MONDE”

Amazon has asked the FCC to approve a 5,105-satellite constellation launching in 2028 that would provide global direct-to-cell "voice, messaging, data, and emergency services," similar to Starlink's partnership with T-Mobile. The network would use Globalstar spectrum, support future Apple satellite services, and complement Amazon's existing Leo broadband constellation. The Verge reports: Advanced Television points out that the FCC application also includes a request to use spectrum assigned to Iridium's satellite network outside the US, even as Rocket Lab is in the process of acquiring Iridium with plans to expand. The new constellation and direct-to-device service will "complement" the broadband services Amazon also plans to offer through its Leo platform. In addition to consumer satellite service, it would also be used for things like disaster response and emergency messaging. Amazon says the new direct-to-device satellites "will process the signals in orbit before relaying them to improve performance." The new constellation will be nearly double the size of Amazon's initial Leo constellation, which is planned to include around 3,200 satellites. As of July 2nd, Amazon says "over 375" of those satellites have launched so far.

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Northrop Grumman has launched a private satellite-servicing mission to attach life-extending "jetpacks" to aging communications satellites in geosynchronous orbit. "It's the second satellite-saving mission to launch this month, all part of a growing, money-saving effort to keep spacecraft running as long as possible," reports Phys.org. From the report: Launched by SpaceX, Northrop Grumman's mission robotic vehicle -- dubbed MRV -- and its jetpacks will spend the next year angling into the proper orbit 22,300 miles (36,000 kilometers) above Earth. Hundreds of satellites orbit at this so-called geosynchronous orbit, where they match the speed of Earth's rotation and keep to the same part of the sky for continuous coverage. Once in place by mid-2027, the minivan-sized spacecraft will use its 10-foot (9-meter) arms to attach a jetpack to an aging communication satellite. Then it will zip off to two more satellites in need. For its debut flight, the spacecraft was accompanied by three electric-propelled jetpacks that peeled away separately following liftoff. Like the MRV, the jetpacks will use their own xenon gas thrusters to get to the desired orbit. Once in place, the jetpacks will wait for the robot to grab them, one at a time, and plug them into their designated satellites. Each jetpack -- the size of a washing machine -- will provide the necessary oomph for an out-of-gas satellite to keep operating for several more years instead of retiring. If it works, it will be a boon for satellite operators SES of Luxembourg and Optus of Australia, saving them millions of dollars in replacement costs.

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A new study proposes using shoebox-sized detector satellites to sniff out nuclear weapons launched by adversary nations. The idea is aimed at addressing fears that a space-based nuclear detonation could destroy satellites across low Earth orbit and make some orbits unusable for years. Space.com shares the findings from a new paper authored by Areg Danagoulian, an associate professor of nuclear science and engineering at the Massachusetts Institute of Technology: No reliable way currently exists to detect and defuse a nuclear bomb in space. Danagoulian proposes a constellation of small "9U" cubesats, each one about the size of a large shoebox and each carrying a special detector capable of sensing radiation emitted by unexploded nuclear bombs. He explores a scenario in which Russia launches a suspected space nuke into an orbit with an altitude of 1,200 miles (2,000 km). That number is not random. In 2022, Russia's Kosmos 2553 satellite, orbiting at that exact altitude, triggered suspicions it might be testing components for a future orbital nuclear weapon. Russia claims the satellite just observes Earth. At that altitude, the satellite passes through the Van Allen belt, a region of intense cosmic radiation trapped by Earth's magnetic field. Most of the belt stretches between altitudes of around 600 miles (1,000 km) to tens of thousands of miles, but in some areas the radiation can reach much closer to Earth's surface. The interaction between the fissile material inside the nuke and the energetic particles from the radiation belt would create distinct signatures, Danagoulian said, which could help confirm whether a suspicious satellite carries a nuke or not. "The thermonuclear weapon would contain a significant amount of uranium," Danagoulian said. "The high-energy protons [in the uranium] would break up when another proton is coming in and shred the nuclei. That would knock out a large number of neutrons. This interaction turns that device into a very intense neutron source that otherwise would not be there." he process is known as proton-induced neutron spallation, which essentially means the ejection of fragments from material triggered by impacts of protons. The detector satellite Danagoulian proposes would have to be able to get quite close to the suspect spacecraft -- a few kilometers. The inspector spacecraft would carry a sensor combining two types of detectors. At the heart of the device is a neutron scintillator, which detects all incoming neutrons and protons. Around it is a "cage of diamond" detector that detects only neutrons -- not protons. Such a set-up helps filter out the particles present in the environment naturally, said Danagoulian. In addition, by using two "planes of neutron detectors," the sensor can determine the direction from which the neutrons arrived. "If the external diamond detector triggers and gives a signal, you can ignore the particle, because it's most likely a proton and not a neutron," said Danagoulian. "Once you identify those neutrons, by having those two detections, you can back project and find out where the neutron came from." Danagoulian says such a nuke sniffer would have to be launched into an orbit aligned with that of the suspicious satellite and creep up as close as 2.5 miles (4 km) from it. It would then take about a week to gather enough measurements to confirm whether the object is hiding a nuke or not. A constellation of 10 such satellites could reduce the process to mere hours, Danagoulian said. If a nuke were detected, the military could then try to jam the satellite's communications link from the ground, making it impossible for the adversary to remotely detonate the bomb. There is currently no technology available to safely defuse a nuclear weapon in space. [...] Danagoulian also suggests that high-grade radiation hardening could improve satellites' chances of surviving a nuclear winter in space. The paper has been published in the journal Nature.

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